Stent with a crush-resistant zone

ABSTRACT

An endoluminal prosthesis system for a branched body lumen comprises a branch vessel prosthesis. The branch vessel prosthesis is deployable within a branch vessel body lumen and comprises a stent having a generally tubular body portion, a flareable proximal end portion, and a coupling portion disposed intermediate the body portion and the flareable portion. The coupling portion is more crush-resistant than the body portion. The flareable proximal end may be disposed within a fenestrated stent graft with coupling portion disposed in the fenestration of the fenestrated stent graft.

RELATED APPLICATIONS

The application is a continuation of U.S. application Ser. No.16/516,523, filed Jul. 19, 2019, which is a continuation of U.S.application Ser. No. 15/008,631, filed Jan. 28, 2016, now U.S. Pat. No.10,357,386, which is a continuation of U.S. application Ser. No.11/810,533, filed Jun. 6, 2007, now U.S. Pat. No. 9,259,336, whichclaims the benefit of the filing date under 35 U.S.C. § 119(e) ofProvisional U.S. Patent Application Serial No. 60/811,159, filed Jun. 6,2006. All of the foregoing applications are hereby incorporated byreference.

BACKGROUND 1. Field Of The Invention

This invention relates to medical devices, and more particularly, toendoluminal devices and methods for making and using such endoluminaldevices.

2. Description Of Related Art

The functional vessels of human and animal bodies, such as blood vesselsand ducts, occasionally weaken or even rupture. For example, an aorticwall can weaken, resulting in an aneurysm. Upon further exposure tohemodynamic forces, such an aneurysm can rupture, resulting in internalbleeding, and often death.

Various interventions have been provided for weakened, aneurysmal,dissected or ruptured vessels, including surgical interventions andendovascular interventions. Endovascular interventions generally includeinserting an endoluminal device or prosthesis such as a stent or stentgraft into the damaged or diseased body lumen to provide support for thelumen, and to exclude damaged portions thereof.

The endovascular prosthesis is delivered in a radially compressedconfiguration using a catheter delivery system. The catheter isintroduced into the lumen system remotely of the repair site and theprosthesis is delivered to the repair site intraluminally. Theprosthesis is then expanded to engage the luminal wall. The prosthesismay provide some or all of the functionality of the original, healthyvessel and may further preserve any remaining vascular integrity.

An example of a prosthesis that may be used for treating damaged ordiseased body lumens is disclosed in PCT Application WO 98/53761, whichis herein incorporated by reference. The prosthesis may include abifurcated stent graft. The stent graft includes a biocompatible graftmaterial and a plurality of longitudinally disposed stents. The stentgraft is designed to span and exclude an aortic aneurysm extendingbetween the iliac and renal arteries. Other prostheses that may be usedinclude non-bifurcated stent grafts for spanning and excluding aorticaneurysms within the abdominal aorta or the thoracic aorta.

Often times, a body lumen may be damaged in an area that includes abranch vessel. For example, there are at least three branch vesselsextending from the abdominal aorta, each leading to various body organs.These branch vessels include the celiac, mesenteric, and renal arteries.When an aneurysm includes or is adjacent to one or more of these branchvessels, the prosthesis system must be able to exclude the aneurysmwhile maintaining fluid flow through the branch body lumen.

Various stent grafts have been provided for repairing main body lumensand spanning branch vessels without occluding fluid flow thereto. Forexample, a main body stent graft may be provided that has one or morefenestrations or apertures in the side wall of the stent graft. Thestent graft can be deployed so that the fenestration is aligned with abranch vessel.

In many cases, particularly where the damaged portion is positioned atthe junction between the main body lumen and the branch body lumen, orwhere the ostium of the branch vessel is damaged, a main stent graft isinsufficient to adequately repair the luminal system. In thesesituations, it may be preferable to provide a branch lumen prosthesisfor positioning within the branch vessel. The branch lumen prosthesismay be used independently, or in conjunction with a main bodyprosthesis.

U.S. Published Patent Application Nos. 2005/0222668, 2005/0171598, and2005/0149166 disclose various systems for repairing branched body lumensystems. Various aspects of each of these disclosures may be used inconjunction with the present invention. U.S. Published PatentApplication Nos. 2005/0222668, 2005/0171598, and 2005/0149166 are hereinincorporated by reference.

A branch vessel prosthesis should be capable of complying with a varietyof challenging and often competing demands. For example, the branchvessel prosthesis should preferably be highly flexible and capable oftracking through and conforming with a highly tortuous luminalenvironment. If the prosthesis includes a balloon-expandable stent, thestent should be sufficiently resilient so as not to hinder balloonexpansion and/or molding.

On the other hand, once the prosthesis is implanted in the body lumen,it must be sufficiently strong and robust to survive a highly dynamicand pulsatile luminal environment that can promote prosthesis damage.This is of particular concern where the branch vessel prosthesis isdeployed within a fenestration of a main body prosthesis. During thecardiac cycle, the main body prosthesis will pulse and move with themain body vessel, placing stress on the branch vessel prosthesis at thefenestration. When the main body prosthesis moves, it can exertsignificant concentrated and localized stresses on the branch vesselprosthesis 11 through the fenestration. Over time, this cyclic wear cancause the branch vessel prosthesis to weaken and eventually to crushunder the force of the main body prosthesis, requiring further medicalintervention.

SUMMARY

According to an aspect of the present invention, an endoluminalprosthesis system for a branched body lumen is provided and comprises abranch vessel prosthesis that is deployable within a branch vessel bodylumen. The branch vessel prosthesis comprises a stent having a generallytubular body portion, a flareable proximal end portion, and a couplingportion disposed intermediate the body portion and the flareableportion. The coupling portion is preferably more crush-resistant thanthe body portion so that the stent can withstand high luminal stressespresent in the ostial region of the vessel branch.

The system may further comprise a main vessel prosthesis that isdeployable within a main vessel body lumen and having a main prosthesislumen and a fenestration for providing fluid communication between themain prosthesis lumen and the branch vessel body lumen. When the mainand branch vessel prostheses are used in cooperation to repair abranched body lumen, the coupling portion of the branch vesselprosthesis may be sized and configured to engage the fenestration. Themain vessel prosthesis may optionally comprise a reinforcing member thatat least partially surrounds a perimeter of the fenestration and isconfigured to engage the coupling portion of the stent. One or both ofthe main and branch vessel prostheses may comprise a graft.

According to another aspect of the invention, a prosthesis system may beprovided that includes a branch vessel prosthesis comprising a bodyportion, a flareable end portion, and a coupling portion. The bodyportion may have a stent configuration comprising at least one bodystent ring including a plurality of interconnected body struts.Likewise, the flareable end portion may have a stent configurationcomprising at least one flare stent ring including a plurality ofinterconnected flare struts.

Such a prosthesis may include a coupling portion having a stentconfiguration comprising at least one coupling stent ring disposedbetween a flare stent ring and a body stent ring. The coupling stentring may comprise a plurality of interconnected coupling struts. In someembodiments, the coupling portion may comprise a plurality of couplingstent rings.

According to another aspect of the invention, the coupling struts may bethicker than the body struts. For example, the coupling struts may beradially and/or circumferentially thicker than the body struts. Thecoupling struts may have a thickness that is at least 10%, at least 20%,or at least 25% thicker than the body struts. In some embodiments, thecoupling struts may be radially and/or circumferentially thicker thanthe flare struts.

According to another aspect of the invention, the body portion maycomprise a plurality of longitudinally-interconnected body stent rings,and the coupling portion may comprise a plurality oflongitudinally-interconnected coupling stent rings. The interconnectionfrequency between the coupling stent rings may be greater than theinterconnection frequency between the body stent rings adjacent thecoupling portion.

In some embodiments, the axial dimension of each of the flare stentrings may be greater than the axial dimension of each of at least twobody stent rings adjacent the flareable end portion. For example, theaxial dimension of the flare stent rings may increase proximally withthe flareable configuration. The axial dimension of each of the flarestent rings may be at least 10%, at least 20%, or at least 40% greaterthan the axial dimension of each of at least two body stent ringsadjacent the flareable end portion. The axial dimension of theproximal-most flare stent ring may be at least 10%, at least 20%, or atleast 25% greater than the axial dimension of the distal-most flarestent ring.

According to yet another aspect of the invention, the body stent ringsmay be interconnected by a plurality of body connector struts and theflare stent rings may be interconnected by a plurality of flareconnector struts. The flare connector struts may be thicker than thebody connector struts. The thickness of the flare connector struts maybe at least 10% greater, at least 20% greater, or at least 25% greaterthan the thickness of the body connector struts. The flare connectorstruts may be radially and/or circumferentially thicker than the bodyconnector struts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a main prosthesis disposedin the abdominal aorta;

FIG. 1A is a partial side cross-sectional view of a branched vesselsystem including a branch vessel prosthesis coupled to a mainprosthesis;

FIG. 1B is a top cross-sectional view of a branch vessel prosthesiscoupled to a main vessel prosthesis;

FIG. 2A is a partial cross-sectional view of a main vessel prosthesis inthe descending aorta having fenestrations aligned with the leftsubclavian artery and the left common carotid artery;

FIG. 2B is a partial cross-sectional view of a main vessel prosthesis inthe descending aorta with a branch vessel prosthesis extending through afenestration into the left subclavian artery;

FIG. 2C is a partial cross-sectional view of a main vessel prosthesis inan iliac artery with a branch vessel prosthesis extending into thehypogastric artery;

FIG. 3 is a partial cross-sectional view of a branch vessel prosthesisdeployed within a fenestration of a main vessel prosthesis;

FIGS. 4 through 4D illustrate partial views of stent configurations thatincorporate various aspects and features within the scope of the presentinvention;

FIG. 5 is a partial view of a proximal portion of a stent configurationhaving a crush-resistant zone;

FIG. 6 is a side perspective view of a delivery device for a branchvessel prosthesis;

FIG. 7 is a cross-sectional view of a distal portion of the deliverydevice of FIG. 6;

FIG. 8 shows a branch vessel prosthesis delivery device inserted into abranch vessel;

FIG. 9 shows the delivery device of FIG. 8 in a partially-deployedstate; and

FIG. 10 shows the delivery device of FIG. 8 in a partially-deployedstate.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the specification, when referring to a prosthesis, or astructure or component of a prosthesis, the terms “distal” and“distally” shall denote a position, direction, or orientation that isgenerally downstream in the direction of fluid flow.

Accordingly, the terms “proximal” and “proximally” shall denote aposition, direction, or orientation that is generally upstream in thedirection of fluid flow. Throughout the specification, when referring toa delivery system for a prosthesis, or a structure or component of adelivery system, the terms “distal” and “distally” shall denote aposition, direction, or orientation that is generally toward thepatient. Accordingly, the terms “proximal” and “proximally” shall denotea position, direction, or orientation that is generally away from thepatient.

The terms “crush-resistant” and “crush-resistance” are used throughoutthe specification and in the appended claims. It is noted that theseterms are intended to refer to the measure of the ability of a structureto withstand plastic deformation when the structure is exposed to aconcentrated and localized stress. The crush-resistance of a stent maybe estimated experimentally by determining the yield strength, or theminimum force required to plastically deform the stent. Crush-resistancemay be a function of material selection, as well as stent structure anddesign.

FIG. 1 illustrates a bifurcated main vessel prosthesis 1 having a distalend 2 and a proximal end 3. The main vessel prosthesis 1 is disposedwithin the abdominal aorta 4 from a point above the renal arteries 5 toa point where the main prosthesis 1 bifurcates into the iliac arteries6. The main vessel prosthesis 1 includes two fenestrations 7 or holesthat are configured to align with the renal arteries 5. The abdominalaorta 4 and the renal arteries 5 form a branched body lumen system.

The main vessel prosthesis 1 preferably includes a generallyfluid-impermeable graft material, for example Dacron. The main vesselprosthesis 1 may further include one or more stents 19, 20. The stents19, 20 may be positioned internally and/or externally of the graftmaterial. The prosthesis 1 may comprise an internal stent 20 at one orboth ends 2, 3. The internal stent 20 provides a smooth externalprosthesis surface and helps seal the end of the main vessel prosthesis1 against an adjoining vascular wall or against an interconnectingmodule.

Stents 19, 20 may include any suitable stent configuration known in theart. The stents 19, 20 may be balloon-expandable or self-expanding. Forexample, stents 19, 20 may comprise self-expanding Z stents. Theprosthesis may comprise a combination of stents 19, 20 or a single stenthaving both balloon-expandable and self-expanding properties. Theinternal stents 20 may comprise barbs (not shown) that extend throughthe graft material to engage the surrounding vessel wall, therebyanchoring the prosthesis 1 to the vessel and preventing movement of themain vessel prosthesis 1 once it is deployed.

The main vessel prosthesis 1 may further include an attachment member 10for securing the main prosthesis 1 to the wall of the main vessel toprevent migration of the main prosthesis 1 after it has been placed. Theattachment member may comprise a bare-wire self-expanding zig zag stentand may include a plurality of radially disposed barbs for engaging theaorta 4.

In FIG. 1, the branched vessel system has a first aneurysm 8 positionedbetween the renal arteries 5 and the iliac arteries 6 and a secondaneurysm 9 positioned in the ostium of the renal arteries 5. The mainvessel prosthesis 1 provides a fluid seal against the main vessel 4 atpositions proximal and distal of aneurysm 8, thereby excluding bloodflow from the damaged area. Fenestrations 7 are provided so that bloodflow is maintained to the renal arteries 5. Main vessel prosthesis 1repairs aneurysm 8 but leaves aneurysm 9 exposed to blood flow andhemodynamic pressure.

Accordingly, a branch vessel prosthesis 11 may be provided in the renalartery 5 to exclude aneurysm 9. FIG. 1A shows a side view of thebranched body lumen system of FIG. 1. The main vessel prosthesis 1 isdisposed within the aorta and extends proximally and distally of therenal arteries 5. The prosthesis 1 has fenestrations 7 that are alignedwith the renal arteries 5 to provide blood flow to the arteries. Abranch vessel prosthesis 11 is disposed within the renal artery 5. Adistal end of the branch vessel prosthesis 11 extends distally into theartery 5 and a proximal end 12 of the prosthesis 11 extends proximallythrough the fenestration 7 into the main vessel prosthesis 1.

FIG. 1B shows a cross-sectional view of the branched body lumen systemof FIGS. 1 and 1A. The branch vessel prosthesis 11 comprises a generallyfluid-impermeable graft material. The branch vessel prosthesis 11 mayoptionally comprise a stent 19 or a plurality of stents. The branchvessel prosthesis 11 seals against the renal artery at a position distalof aneurysm 9. The fenestration 7 forms a seal between the branch vesselprosthesis 11 and the main vessel prosthesis 1 and assists in anchoringthe branch vessel prosthesis 11 in the vasculature. The main vesselprosthesis 1 and the branch vessel prosthesis 11 effectively excludeaneurysm 9.

Various graft materials and configurations may be used for either themain vessel prosthesis 1 or the branch vessel prosthesis 11. Graftconfigurations include, but are not limited to films, coatings, sheetsof biocompatible fabrics, non-woven materials and porous materials.

Examples of biocompatible polymers from which porous sheets can beformed include polyesters, such as poly(ethylene terephthalate),polylactide, polyglycolide and copolymers thereof; fluorinated polymers,such as polytetrafluoroethylene (PTFE), expanded PTFE andpoly(vinylidene fluoride); polysiloxanes, including polydimethylsiloxane; and polyurethanes, including polyetherurethanes, polyurethaneureas, polyetherurethane ureas, polyurethanes containing carbonatelinkages and polyurethanes containing siloxane segments.

In addition, materials that are not inherently biocompatible may besubjected to surface modifications in order to render the materialsbiocompatible. Examples of surface modifications include graftpolymerization of biocompatible polymers from the material surface,coating of the surface with a crosslinked biocompatible polymer,chemical modification with biocompatible functional groups, andimmobilization of a compatibilizing agent such as heparin or othersubstances. Thus, any polymer that may be formed into a porous sheet canbe used to make a graft material, provided the final porous material isbiocompatible. Polymers that can be formed into a porous sheet includepolyolefins, polyacrylonitrile, nylons, polyaramids and polysulfones, inaddition to polyesters, fluorinated polymers, polysiloxanes andpolyurethanes as listed above. Preferably the porous sheet is made ofone or more polymers that do not require treatment or modification to bebiocompatible.

The graft material may include a biocompatible polyurethane. Examples ofbiocompatible polyurethanes include THORALON® (Thoratec, Pleasanton,Calif.), BIOSPAN®, BIONATE®, ELASTHANE™, PURSIL™ and CARBOSIL™ (PolymerTechnology Group, Berkeley, Calif.). As described in U.S. PatentApplication Publication No. 2002/0065552, incorporated herein byreference, THORALON® is a polyetherurethane urea blended with asiloxane-containing surface modifying additive. Specifically, thepolymer is a mixture of base polymer BPS-215 and an additive SMA-300.

The graft material may also include extracellular matrix materials. The“extracellular matrix” is typically a collagen-rich substance that isfound in between cells in animal tissue and serves as a structuralelement in tissues. Such an extracellular matrix is preferably a complexmixture of polysaccharides and proteins secreted by cells. Theextracellular matrix can be isolated and treated in a variety of ways.Following isolation and treatment, it is referred to as an“extracellular matrix material,” or ECMM. ECMMs may be isolated fromsubmucosa (including small intestine submucosa), stomach submucosa,urinary bladder submucosa, tissue mucosa, renal capsule, dura mater,liver basement membrane, pericardium or other tissues.

Purified tela submucosa, a preferred type of ECMM, has been previouslydescribed in U.S. Pat. Nos. 6,206,931, 6,358,284 and 6,666,892 as abio-compatible, non-thrombogenic material that enhances the repair ofdamaged or diseased host tissues. U.S. Pat. Nos. 6,206,931, 6,358,284and 6,666,892 are incorporated herein by reference. Purified submucosaextracted from the small intestine (“small intestine submucosa” or“SIS”) is a more preferred type of ECMM for use in this invention.Another type of ECMM, isolated from liver basement membrane, isdescribed in U.S. Pat. No. 6,379,710, which is incorporated herein byreference. ECMM may also be isolated from pericardium, as described inU.S. Pat. No. 4,502,159, which is also incorporated herein by reference.

In addition to xenogenic biomaterials, such as SIS, autologous tissuecan be harvested as well. Additionally Elastin or Elastin LikePolypeptides (ELPs) and the like offer potential as a material tofabricate the covering or frame to form a device with exceptionalbiocompatibility. Another alternative would be to use allographs such asharvested native valve tissue. Such tissue is commercially available ina cryopreserved state. In addition, a bare metal stent or a coveredstent could be coated with an anti-restenotic agent, such as paclitaxel,sirilomis or other equivalent. In addition, the graft can be coated withan anti-thrombogenic agent, such as heparin.

The graft may be attached to a stent by various means. The graftmaterial may be attached to the stent by stitching, for example by usinga monofilament or braded suture material. The graft material also may beaffixed to the stent by dipping the stent in a liquefied polymer andallowing the polymer to solidify into a film. The liquefied polymer maybe a molten polymer or a polymer or pre-polymer before curing orcross-linking occurs.

FIGS. 2A-2C illustrate additional applications for prosthesis systemsaccording to an aspect of the invention. In FIG. 2A, a main vesselprosthesis 1 is disposed partially within the aortic arch and within thethoracic aorta 14. The prosthesis 1 has fenestrations 7 that generallyalign with the left subclavian artery 15 and the left common carotidartery 16. FIG. 2B shows a main vessel prosthesis 1 having afenestration 7 that aligns with the left subclavian artery 15. A branchvessel prosthesis 11 is provided and extends into the left subclavianartery 15. The branch vessel prosthesis 11 is secured to the main vesselprosthesis 11 through fenestration 7. FIG. 2C shows a main vesselprosthesis 1 disposed within an iliac artery 6. The prosthesis 1 has afenestration 7 that aligns with the hypogastric artery 18. A branchvessel prosthesis 11 is provided and extends into the hypogastric artery18. The branch vessel prosthesis 11 is secured to the main vesselprosthesis 1 through fenestration 7. Numerous other applications for theprosthesis systems described herein are contemplated and are includedwithin the scope of the present invention.

In FIG. 3, a branch vessel prosthesis 11 is deployed within a branchvessel and through the fenestration 7 of a main vessel prosthesis 1. Thefenestration 7 may comprise a reinforcing member 29. The reinforcingmember 29 at least partially surrounds a perimeter of the fenestration 7and is configured to engage the branch vessel prosthesis 11. The member29 helps reinforce the connection and the seal between the main vesselprosthesis 1 and the branch vessel prosthesis 11. The reinforcing member29 may comprise a metal ring or gasket, and may comprise, for example,stainless steel or nitinol.

The branch vessel prosthesis 11 has a proximal end 30 and a distal end32. The prosthesis 11 comprises a generally tubular body portion 33 anda flareable proximal end portion 36. The body portion 33 and theflareable portion 36 are radially disposed about an axis A. The bodyportion 33 is configured to extend distally into the branch lumen. Theflareable portion 36 is configured to extend proximally into the ostiumof the branch vessel. In FIG. 3, the flareable portion 36 extendsproximally through the fenestration 7 and flares radially outwardly intothe lumen of the main vessel prosthesis 1. Preferably, at least a partof the flareable portion 36 has a diameter that is greater than thediameter of the fenestration 7. A bending portion 50 is disposedintermediate the flareable portion 36 and the body portion 33. Thebending portion 50 is configured to bend to allow the flareable portion36 to flare.

The prosthesis 11 further comprises a coupling portion 38. The couplingportion is disposed intermediate the flareable portion 36 and the bodyportion 33. The body portion 33 is generally longer than the couplingportion 38. For example, the body portion 33 may be five to seven timeslonger than the coupling portion 38. The coupling portion 38 isconfigured to engage the fenestration 7 of the main vessel prosthesis 1when the branch vessel prosthesis 11 is deployed. When deployed, thecoupling portion 38 is in mechanical communication with the main vesselprosthesis 1.

The branch vessel prosthesis 11 may comprise a suitable biocompatiblegraft material, as described above. Additionally, or alternatively, theprosthesis 11 may comprise one or more stents 19, as described above.The stents 19 may be fastened to the inner, the outer, or both surfacesof the graft. The graft material may cover the entire prosthesis or itmay cover only a portion of the prosthesis. The stents 19 may beballoon-expandable or self-expanding. Imageable markers 43, such asradiopaque markers, may be attached to or integral with the prosthesis11. For example, an imageable marker 43 may be provided and configuredto indicate the bending portion 50 or the coupling portion 38.

Self-expanding stents can be made of stainless steel, materials withelastic memory properties, such as NITINOL, or any other suitablematerial. A suitable self-expanding stent includes Z-STENTS®, which areavailable from Cook, Incorporated, Bloomington, Ind. USA.Balloon-expandable stents may be made of stainless steel (typically316LSS, CoCr, Etc.). A balloon-expandable stent or stent portion may becombined with a self-expanding stent or stent portion. For example, theprosthesis 11 may comprise a self-expanding body portion 33 and aballoon-expandable flareable portion 36. Alternatively, the prosthesismay comprise a self-expanding flareable portion 36 and aballoon-expandable body portion 33.

The body portion 33 preferably possesses a high degree of flexibilityand resiliency. During delivery, the prosthesis 11 must be capable oftracking tortuous body lumina. Additionally, the prosthesis 11 must besufficiently resilient to allow for ease of balloon expansion. In use,the body portion 33 of prosthesis 11 is exposed primarily to radialcompression due to luminal contraction and expansion. The body portion33 is not exposed to significant crushing or bending loads. Accordingly,the body portion 33 does not require a high degree of crush-resistance.

The flareable portion 36 preferably possesses a high degree offlexibility and resiliency as well. To deploy the branch vesselprosthesis 11, the flareable portion 36 is expanded and flared into theostium of the branch vessel or into the lumen of the main vesselprosthesis 1. This is typically accomplished by using an expandableballoon to plastically deform or “iron” the flareable portion 36 from atubular configuration into a flared configuration. If the flareableportion 36 is flexible, it will be relatively easy to flare. Conversely,if the flareable portion 36 is too rigid, it may be difficult to deploy.The flareable portion 36 does not require a high degree ofcrush-resistance because once the prosthesis 11 is deployed, theflareable portion 36 does not receive significant loading.

The coupling portion 38, on the other hand, preferably comprises a highdegree of crush-resistance. In use, the cardiac cycle causes the mainvessel prosthesis to pulse and to move along its axis. The distal end ofthe branch vessel prosthesis 11 is anchored within the branch lumen andthe proximal end of the prosthesis 11 is anchored by the main vesselprosthesis 1 within the fenestration 7. As the main vessel prosthesis 1pulses, it exerts a concentrated stress on the coupling portion 38through the fenestration 7. This stress is particularly great where thefenestration 38 comprises a reinforcing member 29 such as a nitinolring. The stress causes the prosthesis to bend, resulting in tensile,compression, and shear strain in the region adjacent the fenestration.Over time, this pulsatile stress can cause the coupling portion 38 toplastically deform and to crush under the weight of the main vesselprosthesis.

It is important to note that crush-resistance, as used herein, is notsynonymous with radial strength. The radial strength of an expandedprosthesis is a measure of its ability to withstand elastic deformationwhen exposed to a uniform distributed radial stress. As noted above, thecrush-resistance of an expanded prosthesis, on the other hand, is ameasure of its ability to withstand plastic deformation when exposed toa concentrated and localized stress that includes bending. A prosthesismay comprise significant radial strength but have poor crush-resistance.Conversely, a prosthesis may comprise very low radial strength but havehigh crush-resistance.

A branch vessel prosthesis 11 may be provided that includes a stent 48.FIG. 4 shows a partial view of a stent 48 according to an aspect of theinvention. The stent 48 is preferably balloon-expandable although aself-expanding or a hybrid balloon/self-expanding stent may be provided.The branch vessel prosthesis 11 may optionally include a graft that hasbeen attached to the stent as described above. The prosthesis 11 issuitable for being deployed in the ostium of a vessel system. Theprosthesis 11 may be used independently, for example to support or tostent the ostium of the branch vessel. Alternatively, the prosthesis 11may be used in conjunction with a main vessel prosthesis, as describedabove.

The stent 48 is generally tubular and has a proximal end 30 and a distalend 32. The stent 48 includes a flareable portion 36 and a body portion33. The flareable portion 36 is disposed at the proximal end 30 of thestent 48. The body portion 33 is disposed distally of the flareableportion 36. The body portion 33 and the flareable portion 36 areradially disposed about an axis A. The body portion 33 is coupled to theflareable portion 36 via bending portion 50. The bending portion 50 isconfigured to bend to allow the flareable portion 36 to flare radiallyoutwardly during deployment.

The body portion 33 comprises a stent configuration that includes atleast two longitudinally interconnected body stent cells 54. In theembodiment shown in FIG. 4, the body portion 33 includes at least eightinterconnected cells 54. The body portion 33 may include a fewer or agreater number of cells 54 according to the particular application. Eachof the cells 54 may include a substantially circular stent ringcomprising an endless undulating pattern, as shown in FIG. 4. Each ofcells 54 is radially disposed about the axis A and longitudinallydisposed with respect to another cell 54. Each of the cells 54 includesa plurality of proximally-oriented peaks P and a plurality ofdistally-oriented valleys V. The body cells 54 are arranged in analternating pattern so that peaks in one body cell 54 areaxially-aligned with valleys in an adjacent body cell 54. Each of thebody cells 54 comprises an axial dimension Db. In the embodiment shownin FIG. 4, each of the body cells 54 has a substantially equal axialdimension Db.

Adjacent body cells 54 are interconnected by struts 75 and/or connectionmembers 76. In FIG. 4, axially-oriented struts 75 interconnect adjacentbody cells 54 between a peak of one body cell 54 and a valley of adistally-adjacent body cell 54. Connection members 76 interconnectadjacent body cells 54 between a valley of one body cell 54 and a peakof a distally-adjacent body cell 54. Struts 75 and connection members 76provide structural support and elasticity to the body portion 33.

Flexibility of the body portion 33 along the body cells 54 may beprovided in many ways. For example, the shape of connection members 76may be varied to affect the flexibility of the body portion 33. Theconnection member 76 may comprise an “I” shape, a “V” shape, an “S”shape, a “W” shape, or any other arcuate or undulating shape. The numberand configuration of the struts 75 can also be varied to affect theflexibility of the body portion 33. For example, increasing thefrequency of struts 75 results in generally lower flexibility whiledecreasing the frequency of struts 75 results in generally higherflexibility. Further, the body portion 33 may be made more flexible bydecreasing the thickness of any of the struts 75, or connection members76.

The flareable portion 36 comprises a stent configuration that includesat least two longitudinally interconnected flare cells 60. Each of theflare cells 60 may include a substantially circular stent ringcomprising an endless undulating pattern, as shown in FIG. 4. Each ofthe flare cells 60 is radially disposed about the axis A andlongitudinally disposed with respect to another cell 60. Each of thecells 60 includes a plurality of proximally-oriented peaks P and aplurality of distally-oriented valleys V. The flare cells 60 arearranged in an alternating pattern so that peaks in a flare cell 60 areaxially-aligned with valleys in an adjacent flare cell 60. The flarecells 60 may be arranged so that the peaks in the distal-most flare cell60 are aligned with the valleys in the proximal-most body cell 54. Eachof the flare cells 60 comprises an axial dimension Df1, Df2.

According to an aspect of the present invention, the axial dimensionDf1, Df2 of the flare cells 60 is generally greater than the axialdimension Db of the body cells 54. Because the axial dimension Df1, Df2of the flare cells 60 is generally greater than the axial dimension Dbof the body cells 54, the flare cells 60 will tend to be more resilientand will be expandable to a larger diameter than the body cells 54. Theproximal peaks of the flareable portion 36 are unattached and are freeto expand and separate, thereby permitting the flareable portion 36 toflare-out in the expanded configuration.

As shown in FIG. 4, the axial dimension Df1 of the proximal-most flarecell 60 is generally greater than the axial dimension Df2 of thedistal-most flare cell 60. Accordingly, the proximal-most flare cell 60will be more resilient and will be expandable to a larger diameter thanthe distal-most flare cell 60. The flare cells 60 are arranged so thatthe axial dimension of the cells increases proximally with the stentconfiguration.

The axial dimensions of each of the flare cells can be selected toprovide a desired flare profile upon deployment.

According to an aspect of the invention, the axial dimension Df1, Df2 ofeach of the flare cells 60 is at least 10% greater or at least 20%greater than the axial dimension Db of the body cells 54. In a preferredembodiment, the axial dimension Df1, Df2 of each of the flare cells 60is at least 40% greater than the axial dimension Db. The axial dimensionDf1 of the proximal-most flare cell 60 may be at least 10% or at least20% greater than the axial dimension Df2 of the distal-most flare cell60. In a preferred embodiment, the axial dimension Df1 is at least 25%greater than axial dimension Df2.

Adjacent flare cells 60 are interconnected by struts 77. In theembodiment shown in FIG. 4, axially-oriented struts 77 interconnectadjacent flare cells 60 between a peak of the proximal-most flare cell60 and a valley of the distal-most flare cell 60. Struts 77 providestructural support and stiffness to the flareable portion 36.

The flareable portion 36 is coupled to the body portion 33 through thebending portion 50. The bending portion 50 minimizes the stress imposedby the flareable portion 36 on the tubular portion 33 in the expandedconfiguration by providing a region of relative flexibility. Increasingthe flexibility of bending portion 50, increases the ability of theflareable portion 36 to flare-out in the expanded configuration. Flaringof the flareable portion 36 is thus facilitated by the bending portion50.

The bending portion 50 may comprise at least two bendable connectorelements 52 that connect the flareable portion 36 to the body portion33. The number of connector elements 52, and therefore the frequency ofthe points of attachment between the flareable portion 36 and the bodyportion 33 can be varied to facilitate bending in the bending portion50.

Connector elements 52 may be non-linear or arcuate in shape, asillustrated in FIG. 4, or may be generally linear as illustrated inFIGS. 4A-C. Connector elements 52 may, for example, comprise a “V”shape, an “S” shape, or a “W” shape. Where the prosthesis 11 comprises agraft material, for example a coating or film of plastic (such asThoralon), the bending portion 50 may include the graft. For example,the flareable portion 36 and the body portion 33 may comprise separatestent structures that are longitudinally displaced from each other andare connected through the graft. In FIG. 4, the connector elements 52are disposed between a valley of the distal-most flare cell 60 and apeak of the proximal-most body cell 54.

According to an aspect of the invention, the flare struts 77 may bethicker than the body struts 75. The flare struts 77 may becircumferentially thicker than the body struts 75 and have a thicknessmeasured along the circumference of the stent 48 that is greater than alike thickness of the body struts 75. In other words, the flare struts77 may be wider than the body struts 75. The flare struts 77 mayalternatively or additionally be radially thicker than the body struts75. That is to say, the flare struts 77 may have a thickness measuredalong a radius of the stent 48 that is greater than a like thickness ofthe body struts 75. The flare struts 77 may be at least 10% or at least20% thicker than the body struts 75. In a preferred embodiment, theflare struts 77 are at least 25% thicker than the body struts.

Thickening the flare struts 77 in relation to the body struts 75 willgenerally reduce the flexation and increase the stiffness of theflareable portion 36 in relation to the body portion 33. Because theproximal peaks of the flareable portion 36 are unattached and are freeto expand and separate, the flareable portion 36 is most flexible andresilient at its proximal end. Further, because the axial dimension Df1of the proximal-most flare cell 60 is greater than the axial dimensionDf2 of the distal-most flare cell 60, the flexibility of theproximal-most cell will be generally greater and the stiffness will begenerally less than that of the distal-most flare cell. Consequently, inthe embodiment shown in FIG. 4, the stiffness of the flareable portion36 increases distally towards the bending portion 50, thereby forming agenerally crush-resistant zone at the distal end of the flareableportion 36. This crush-resistant zone is desirable, particularly wherethe prosthesis 11 requires additional strength and support, for examplein the ostium of the branch vessel, or at the region in contact with thefenestration 7 of a main vessel prosthesis 1.

FIG. 4A illustrates another stent 48 according to an aspect of thepresent invention. The stent 48 includes a flareable portion 36 and abody portion 33. The flareable portion 36 is disposed at the proximalend 30 of the stent 48. The body portion 33 is disposed distally of theflareable portion 36. The body portion 33 and the flareable portion 36are radially disposed about an axis A. The body portion 33 is coupled tothe flareable portion 36 through bending portion 50. The bending portion50 is configured to bend to allow the flareable portion 36 to flareradially outwardly.

The stent 48 further comprises a coupling portion 38. The couplingportion 38 is positioned generally intermediate the body portion 33 andthe flareable portion 36 and may comprise the bending portion 50. Thecoupling portion 38 is configured to support the ostium of a branchvessel or to engage the fenestration 7 in the main vessel prosthesis 1.The main vessel prosthesis 1 can be secured to the branch vesselprosthesis 11 via the coupling portion 38.

The stent 48 comprises at least one imageable marker 43. The imageablemarker 43 is disposed on the branch vessel prosthesis 11 and isconfigured to indicate a portion of the prosthesis 11. The imageablemarker 43 comprises a substance that is imageable in the body using, forexample fluoroscopic techniques. For example, the marker may comprisegold. In FIG. 4A, the stent 48 comprises a plurality of markers 43disposed radially about the prosthesis that generally indicate thecoupling portion 38. Each of the imageable markers 43 is in the shape ofan eyelet.

The body portion 33 comprises a plurality of axially-orientedinterconnected body cells 54. Each body cell 54 may include asubstantially circular stent ring comprising an endless undulatingpattern. Each body cell 54 comprises a plurality of interconnected bodystruts 55. Adjacent body struts 55 interconnect to formproximally-oriented peaks P and distally-oriented valleys V. Body cells54 have an axial dimension Db. Adjacent body cells 54 are interconnectedby a plurality of axially-oriented struts 75 and/or connection members76, as previously described.

The flareable portion 36 comprises at least two flare cells 60. Theflare cells 60 are configured to flare when the prosthesis 11 is in anexpanded configuration. Each flare cell 60 includes a substantiallycircular stent ring comprising an endless undulating pattern. Each flarecell 60 comprises a plurality of interconnected flare struts 61.Adjacent flare struts 61 form proximally-oriented peaks anddistally-oriented valleys. The axial dimension Df1, Df2 of the flarecells 60 is generally greater than the axial dimension Db of the bodycells 54, as described above. Further, the axial dimension Df1 of theproximal-most flare cell 60 is generally greater than the axialdimension Df2 of the distal-most flare cell.

The bending portion 50 comprises a plurality of bendable connectorelements 52. Connector elements 52 connect the flareable portion 36 tothe body portion 33. The number of connector elements 52, and thereforethe frequency of the points of attachment between the flareable portion36 and the body portion 33 can be varied to facilitate bending in thebending portion 50. The shape of the connector elements 52 can also bemodified, as described above to selectively increase or decreaseflexibility in the bending portion.

The coupling portion 38 is disposed intermediate the body portion 33 andthe flareable portion 36. The coupling portion 38 comprises couplingcells 72. Each coupling cell 72 may include a substantially circularstent ring comprising an endless undulating pattern. Each coupling cell72 comprises a plurality of interconnected struts 73. Adjacent couplingstruts 73 form proximally-oriented peaks and distally-oriented valleys.In FIG. 4A, the stent 48 includes two coupling cells 72: one disposedproximally of the bending portion 50, and the other disposed distally ofthe bending portion 50.

The coupling portion 38 is more crush-resistant than the body portion 33and the flareable portion 36. For example, the coupling struts 73 may begenerally thicker than body struts 55 and flare struts 61, as shown inFIGS. 4A and 5. Additionally, connector elements 52 may be thicker thanbody struts 55 and flare struts 61 as shown in FIGS. 4A and FIG. 5.Increasing the thickness of coupling struts 73 and the connectorelements 52 increases the stiffness of the coupling portion 38.Consequently, the coupling portion 38 will be more resistant to bendingand plastic deformation. The body portion 33 and the flareable portion36, on the other hand comprise struts 55, 61 that are thinner and areconsequently more flexible.

The coupling portion 38 preferably comprises struts 73 and connectorelements 52 that are at least 10% thicker than the body struts 55 or theflare struts 61, or the coupling portion 38 may comprise struts 73 andconnector elements 52 that are at least 20% thicker than the body struts55 and the flare struts 61. According to a preferred embodiment, thecoupling portion 38 comprises struts 73 and connector elements 52 thatare at least 25% thicker than the body struts 55 and the flare struts61. The body struts 55 may have a thickness that is generally equal to athickness of the flare struts 61. Alternatively, the body struts 55 mayhave a thickness that is less than or greater than a thickness of theflare struts 61.

FIG. 5 shows a portion of the stent 48 of FIG. 4A, wherein the couplingstruts 73 are circumferentially thicker than the body struts 55. Thecoupling struts 73 may alternatively or additionally be radially thickerthan the body struts 55. As illustrated in FIGS. 4A and 5, the thicknessof each strut 73 and/or connector element 52 may be generallylongitudinally uniform. Alternatively, the struts 73 and/or connectorelements 52 may have a longitudinally variable thickness. For example,the struts 73 and/or connector elements 52 could be configured so that amedial portion comprises a first thickness that is generally greaterthan a second thickness at each end.

FIGS. 4B-4D illustrate alternative stents 48 according to variousaspects of the present invention. Each of the stents 48 includes a bodyportion 33, a proximally disposed flareable portion 36, a bendingportion 50, and a coupling portion 38, as described above with respectto FIGS. 4, 4A and 5. The embodiments shown in FIGS. 4B and 4C include aplurality of radially disposed imageable markers 43 that are configuredto indicate the coupling portion 38 of the prosthesis 11. The imageablemarkers 43 are in the shape of an eyelet. The flareable portion 36 andthe body portion 33 are connected at various points via the eyelets 43and via bendable connector elements 52.

In each of FIGS. 4B-4D, the stent 48 has a coupling portion 38 that ismore crush-resistant than a body portion 33. For example, the couplingstruts 73 may be circumferentially and/or radially thicker than the bodystruts 55. The stents 48 in FIGS. 4B-4D incorporate various additionalfeatures that can be used in the present invention. For example, theinterconnection frequency between adjacent coupling cells 72 may begenerally greater than the interconnection frequency between adjacentbody cells 54. As used herein, “interconnection frequency” refers to thenumber of points of attachment between adjacent cells per unit.

In FIGS. 4B-4D, the interconnection frequency between the body cells 54increases proximally along the stent 48. For example, as shown in FIG.4B, the interconnection frequency increases from one connection per unitU at the distal end of the body 33 portion to two connections per unit Uadjacent the coupling portion 38. The interconnection frequency betweenthe coupling cells 72, on the other hand is four connections per unit.Because the interconnection frequency between the body cells 54 isrelatively low, the body portion 33 will tend to be more flexible thanthe coupling portion. On the other hand, because the interconnectionfrequency between the coupling cells 72 is relatively high, the couplingportion 38 will be better equipped to receive and disperse contactloading from the fenestration 7, and will be generally morecrush-resistant.

FIGS. 6 and 7 illustrate a device 80 for delivering and deploying apartially or entirely balloon expandable branch vessel prosthesis 11into a body lumen. As shown in FIG. 6, the delivery device 80 used toplace and deploy the branch vessel prosthesis 11 comprises a ballooncatheter 82 having a proximal portion 84 and a distal portion 86. Thedistal portion 86 is configured to be percutaneously inserted into apatient to deliver the prosthesis 11 to a damaged or diseased bodylumen. The proximal portion 84 remains outside of the patient and ismanipulated by the operator during a procedure.

FIG. 7 shows a partial cross-sectional view of a distal portion 86 ofthe balloon catheter 82. The balloon catheter 82 comprises a guide wirelumen 96 and a balloon inflation lumen 97. The guidewire lumen 96 isadapted to receive a guidewire 98 during a procedure. The ballooninflation lumen 97 is adapted to deliver pressurized fluid to expand theballoon. As shown in FIG. 6, the proximal portion 84 of the deliverydevice 80 comprises a guidewire port 83 for inserting the guidewire 98into the guidewire lumen 96 and a balloon inflation port 85 forintroducing pressurized fluid into the inflation lumen 97.

The balloon catheter 82 further includes a stent loading area 88 and mayinclude a stent positional indicator system 91 located on a distalportion 86 of the catheter 82. The stent-loading area 88 comprises aninflatable balloon 90. The prosthesis 11 is loaded onto the deflatedballoon 90 in a compressed configuration. The positional indicatorsystem 91 includes one or more positional indicators that correspondwith various parts of the branch vessel prosthesis 11. For example, thepositional indicator system 91 may include an indicator 92 on thecatheter that corresponds with the coupling portion 38. The system 91may further include indicators 93, 94 that correspond with the distaland proximal ends 30, 32 of the prosthesis 11 respectively. Indicators92, 93, 94 may include radiopaque marker bands.

The positional indicator system 91 can be used in conjunction with otherpositional systems for deploying the branch vessel prosthesis 11. Forexample, the main vessel prosthesis 1 may include a positional indicatorthat indicates the position of the fenestration 7. During delivery anddeployment, the indicator 92 may be coordinated with the fenestrationindicator to ensure proper alignment and positioning of the branchvessel prosthesis 11 with respect to the main vessel prosthesis 1.Preferably, the positional indicators 92, 93, 94 are shaped so as toindicate the position and orientation of the branch vessel prosthesis 11during and after deployment. The positional markers may be of anyconfiguration to facilitate their visualization. For example, thepositional markers may be v-shaped with one leg longer than the other.

In operation, the branch vessel prosthesis 11 is positioned about theunexpanded balloon on the catheter and crimped thereto so that desiredportions of the branch vessel prosthesis 11 align with correspondingcomponents of the positional indicator system 91. If the positionalindicators 92, 93, 94 are disposed on the distal portion 86 of thecatheter 82 within the balloon, the balloon 90 may comprise a generallytransparent material so that the marker system 91 can be easily viewedduring loading.

The balloon catheter 82 may comprise any balloon configuration suitablefor expanding the prosthesis 11 and for flaring the flareable portion36. For example, the balloon may comprise a first balloon portion forexpanding the body portion 33 and the coupling portion 38, and a secondballoon portion for further expanding the flareable portion 36. U.S.Published Patent Application Nos. 2005/02222668, 2005/0171598, and2005/0149166, which have previously been incorporated by reference,disclose delivery systems for endoluminal prostheses having single andmultiple balloons. The delivery systems disclosed therein could be usedwith the present invention.

FIGS. 8-10 illustrate various stages of deployment of the branch vesselprosthesis 11. A main vessel prosthesis 1 has previously been deployedwithin the main body lumen and is positioned so that fenestration 7generally aligns with the opening of branch vessel 5. The main vesselprosthesis 1 can be deployed in any manner known in the art, includingthe method described in PCT Application WO 98/53761.

Once the main vessel prosthesis 1 has been deployed, the branchprosthesis delivery device 80 can be inserted via a surgical cut-downinto an artery, or by percutaneous access techniques that are well knownin the art. The branch vessel delivery device 80 is advanced into thedesired position over a stiff wire guide using endoluminalinterventional techniques. A guide wire 98 is introduced into an arteryof the patient and advanced through the lumen of the main vesselprosthesis 1 until its tip is beyond the desired deployment region. Forexample, the guide wire 98 may be advanced into the lumen of the mainvessel prosthesis 1 and distally through the fenestration 7 into thebranch vessel 21. The delivery device 80 is then advanced over the guidewire 98 and into the body lumen until the prosthesis 11 is properlypositioned in the branch vessel 5.

FIG. 8 shows the delivery device 80 positioned within the lumen of themain vessel prosthesis 1 with the branch vessel prosthesis 11 extendingthrough the fenestration 7 into the branch vessel 5. Using standardradiographic techniques, the operator may ensure proper positioning byaligning the prosthesis 11 with the fenestration 7. For example, themain vessel prosthesis may comprise a positional indicator (not shown)that generally indicates the fenestration 7. Radiopaque marker 43,located on the stent, and/or positional indicator 92 located on thedelivery device 80, may be coordinated with a fenestration indicator toensure proper positioning and orientation of the branch vesselprosthesis 11 with respect to the main vessel prosthesis 1. Once theprosthesis 11 is properly positioned, the delivery device 80 is readyfor deployment.

FIG. 9 shows the delivery device 80 with the prosthesis 11 in apartially-deployed state. In FIG. 9, the balloon catheter 82 comprises asingle balloon 90, however multiple-balloon configurations may be used.Pressurized fluid is charged to the balloon 90 via the balloon inflationlumen (not shown), causing the balloon 90 to inflate to a first expandedstate. The balloon 90 expands, causing the prosthesis 11 to radiallyexpand so that the distal end 32 of the prosthesis 11 engages the innerlumen of the branch vessel 5. The distal end 32 of the prosthesis 11 maycomprise barbs (not shown) for securing the prosthesis to the branchvessel 5. At this point, the prosthesis 11 has a generally tubularshape. The flareable portion 36 is not yet flared and the couplingportion 38 is not yet coupled to the main vessel prosthesis 1.

In FIG. 10, the operator has inflated the balloon 90 to expand it to asecond expanded state, thus causing the bending portion 50 of theprosthesis 11 to bend and the flareable portion 36 to flare. As theballoon 90 expands, the coupling portion 38 engages the fenestration 7.Where the prosthesis 11 comprises a graft, the fenestration 7 may form afluid seal between the main vessel prosthesis 1 and the branch vesselprosthesis 11. At this point, the delivery device 80 is ready to beremoved. The balloon 90 is deflated and the catheter 82 is withdrawnfrom over the guidewire 98. A separate balloon catheter may optionallybe used at this point to further mold and iron the flareable portion 36to ensure proper engagement between the main vessel prosthesis 1 and thebranch vessel prosthesis 11. The deployment method, including theinitial expanding step and the flaring step may be performed using asingle delivery catheter as described above. Alternatively, the methodcould be performed using multiple delivery and balloon catheters.

Throughout this specification various indications have been given as topreferred and alternative embodiments of the invention. However, itshould be understood that the invention is not limited to any one ofthese. It is therefore intended that the foregoing detailed descriptionbe regarded as illustrative rather than limiting, and that it beunderstood that it is the appended claims, including all equivalents,that are intended to define the spirit and scope of this invention.

1-20. (canceled)
 21. A balloon expandable stent graft comprising: agenerally tubular body of graft material and at least one stentstructure coupled to the generally tubular body of graft material, thestent structure comprising: a generally tubular body portion comprisinga plurality of rows of cells disposed circumferentially about thegenerally tubular body, each row of cells having an axial dimension, aflareable proximal end portion having an axial dimension and comprisinga plurality of cells disposed circumferentially about the generallytubular body and including at least two longitudinally interconnectedflare cells, and a crush resistant region disposed at the distal end ofthe flareable proximal end portion and proximal of the generally tubularbody portion, wherein the axial dimension of the flareable proximal endportion is greater than the axial dimension of each of the cells of theplurality of rows of cells of the generally tubular body portion, andwherein the crush resistant region is more crush-resistant than the bodyportion such that the crush resistant region is more resistant toplastic deformation than the body portion when exposed to a concentratedand localized stress.
 22. The balloon expandable stent graft of claim21, wherein the flareable proximal end and the generally tubular bodyportion comprise separate stent structures that are longitudinallydisplaced from each other and connected through the graft material. 23.The balloon expandable stent graft of claim 21, wherein the crushresistant region is configured to align with a fenestration of apreviously placed fenestrated main graft and is configured to dispersecontact loading from the fenestration.
 24. The balloon expandable stentgraft of claim 21, wherein the balloon expandable stent graft isdisposed over a balloon of a delivery device comprising a firstpositional indicator aligned with the proximal end of the balloonexpandable stent graft, a second positional indicator aligned with thecrush resistant region and a third positional indicator aligned with thedistal end of the balloon expandable stent graft.
 25. The balloonexpandable stent graft of claim 21, wherein the cells of the at leasttwo longitudinally interconnected connected flare cells have peaks andvalleys and are arranged in an alternating pattern so that peaks in aflare cell are axially-aligned with valleys in a longitudinally adjacentflare cell.
 26. The balloon expandable stent graft of claim 21, whereinthe balloon expandable stent graft is disposed over a balloon of adelivery device and wherein the balloon has a first region with aninflated diameter and a second region having an inflated diametergreater than the first inflated diameter.
 27. The balloon expandablestent graft of claim 26, wherein the first region is configured toengage and expand the tubular body portion of the stent graft and thesecond region is configured to engage and flare the flareable proximalend portion.
 28. A balloon expandable stent graft configured to beplaced within a fenestration of a previously placed main body graft,comprising: a generally tubular body of graft material; a stentstructure coupled to the graft material, the stent structure comprising:a generally tubular body portion; a flareable proximal end portionhaving a proximal end configured to extend through the fenestration, adistal end, and at least two longitudinally interconnected flare cells,a crush resistant region disposed at the distal end of the flareableproximal end portion and proximal of the body portion and configured toextend within the fenestration and to disperse contact loading from thefenestration; wherein the crush resistant region is more crush-resistantthan the body portion such that the crush resistant region is moreresistant to plastic deformation than the body portion when exposed to aconcentrated and localized stress.
 29. The balloon expandable stentgraft of claim 28, wherein the flareable proximal end and the bodyportion comprise separate stent structures that are longitudinallydisplaced from each other and connected through the graft.
 30. Theballoon expandable stent graft of claim 28, wherein the balloonexpandable stent graft is disposed over a balloon of a delivery devicecomprising a first positional indicator aligned with the proximal end ofthe stent graft, a second positional indicator aligned with the crushresistant region and a third positional indicator aligned with thedistal end of the stent graft.
 31. The balloon expandable stent graft ofclaim 28, wherein the at least two longitudinally connected flare cellsare arranged in an alternating pattern so that peaks in a flare cell areaxially-aligned with valleys in a longitudinally adjacent flare cell.32. The balloon expandable stent of claim 21, wherein the graft materialof the generally tubular body covers the entire stent structure.
 33. Theballoon expandable stent of claim 28, wherein the graft material of thegenerally tubular body covers the entire stent structure.
 34. Theballoon expandable stent of claim 22, wherein the generally tubular bodyportion comprises separate stent structures.
 35. The balloon expandablestent of claim 29, wherein the generally tubular body portion comprisesseparate stent structures.
 36. A balloon expandable stent graftcomprising: a generally tubular body of graft material and at least onestent structure coupled to the generally tubular body of graft material,the stent structure comprising: a generally tubular body portioncomprising a plurality of rows of cells, each row of cells having anaxial dimension, a proximal end portion having an axial dimension andcomprising a plurality of cells, wherein at least a portion of theproximal end portion is configured to flare outwardly upon applicationof an external flaring force, and a crush resistant zone disposed at thedistal end of the proximal end portion and proximal of the generallytubular body portion and configured to engage a fenestration of apreviously placed fenestrated device and to disperse contact loadingfrom the fenestration; wherein the crush resistant zone is morecrush-resistant than the generally tubular body portion such that thecrush resistant zone is more resistant to plastic deformation than thebody portion when exposed to a concentrated and localized stress. 37.The balloon expandable stent graft of claim 36, wherein the flareableproximal end and the generally tubular body portion comprise separatestent structures that are longitudinally displaced from each other andconnected through the graft material.
 38. The balloon expandable stentof claim 36, wherein the graft material of the generally tubular body atleast partially covers the stent structure.
 39. The balloon expandablestent of claim 38, wherein the graft material of the generally tubularbody entirely covers the stent structure.
 40. A balloon expandable stentgraft comprising: a generally tubular body of graft material and atleast one stent structure coupled to the generally tubular body of graftmaterial, the stent structure comprising: a generally tubular bodyportion comprising a plurality of rows of cells, each row of cellshaving an axial dimension, a proximal end portion comprising a pluralityof cells, a flareable zone adjacent a proximal end of the proximal endportion and a crush resistant zone disposed distal of the proximal endof the proximal end portion and proximal of the generally tubular bodyportion and configured to engage a fenestration of a previously placedfenestrated device and to disperse contact loading from thefenestration; wherein the crush resistant zone is more crush-resistantthan the generally tubular body portion such that the crush resistantzone is more resistant to plastic deformation than the body portion whenexposed to a concentrated and localized stress.